Thread: Belt speed ?
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Old 01-15-2012, 12:51 PM
DKheld DKheld is offline
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Default Belt speed ?

Problem - damper on the Tbird is going south - chunks of rubber flying everywhere. Thought at first the belt speeds were different on the new A/C set up but the pulley calc says no.
May be the new flex fan is putting lots of resistance on the damper and causing it to separate since it is 50 years old? LOTS more air movement with that new fan so lots more resistance. The fan is driven off the water pump (no clutch) which is driven from 2 belts off the damper. The empty belt groove on the water pump is where the A/C belt will go when I install the compressor this summer. Don't want to change the belt config if I don't have to but don't want to ruin a new replacement damper either. Dang it.

I used 7 inches as my crank pulley diameter and 5 inches for the PS pulley size (probably close). 800 rpm on the large pulley (crank speed at idle) - belt speed is 1466.1rpm. PS pulley running 1120 rpm.

Next I used the same settings but 3 inches for the gen pulley (just for round numbers - probably close there too) Belt speed is still 1466.1rpm but the change is the gen pulley speed which is now around 1866.7 rpm.

Pretty much like I had figured when I was putting it together - that the belt speed is constant and only the pulley speeds change. Not sure if the other 7 inch pulley on the water pump makes a difference - don't think it would since it is the same size as the crank pulley.
Center measurement doesn't make any difference except on the belt length - not concerned about that.

Am I missing something?

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